Consequently, errors must also be reported SB203580 in tables of rates and KIE data to allow the reader to validate the analysis and to further use the data in different analyses or for comparison to new findings. Additionally, clear information regarding the conditions, attempts to assess intrinsic values, and other data processing or manipulation should be reported for experimental KIEs to be compared to values calculated by computer-based simulation, and to be compared to similar measurements conducted by other researchers, or the same researchers using a different assay. Examples of propagation, calculation and reporting

of errors are detailed below. This paper will begin with general considerations of reporting isotope effects on enzymes that will include brief descriptions of intrinsic versus observed KIEs. This section will be followed with a general discussion of error analysis and cases where the conclusions drawn are stringently dependent Lumacaftor on the analysis and its statistics. Methods for data fitting to theoretical models by non-linear regression and plotting of data as function of different parameters will then be outlined and examples will be given to illustrate the importance of a rigorous error analysis. Finally, the recommendations in this report will be summarized in the

concluding remarks. It is hoped that the suggestions put forth here will standardize the reporting of data in the field and further the pursuit of our understanding enzymatic catalysis. A reported KIE measurement should

be either narrative in nature (e.g., H/D KIE on a single turnover rate), or be denoted as a superscript preceding the rate constant that is described. The superscript should specify the heavy isotope that was used and the rate constant should be reported using STRENDA׳s requirements (Apweiler et al., 2010). Thus, an oxygen KIE (k16O/k) should be reported as 18Okcat,18O(kcat/Km), 18Okchem, etc. For solvent KIEs the heavy solvent used should be denoted in the superscript, thus a D2O isotope effect should be denoted as D2OkX. In mixed labeling experiments the isotopic labeling is specified by subscripts of the Molecular motor general form ki,j, where isotope i is in the primary position and isotope j is in the secondary position. A kHH/kTH designation, for example, would describe a primary H/T KIE with hydrogens at the secondary position of both molecules, whereas kHH/kTT would indicate a primary H/T and secondary H/T KIEs in the same measurements. The isotopic labeling of the substrates can be designed so most of the measured KIE will reflect a specific kinetic and mechanistic step such as binding or bond cleavage (Agrawal and Kohen, 2003, McCracken et al., 2004, Markham et al., 2004 and Schramm, 2007).